1. Field Of The Invention
The present invention relates to stable graft copolymer dispersions of low viscosity and superior particle size distribution. More particularly, the invention relates to graft copolymer dispersions prepared by the in situ polymerization in the presence of a free radical catalyst of a vinyl monomer in a polyol.
2. Prior Art
Graft copolymer dispersions prepared from vinyl monomers and polyether polyols and the use thereof in the preparation of polyurethane polymers are well known in the art as evidenced by U.S. Pat. Nos. 3,383,351 and 3,652,659. These patents disclose various methods of preparing graft copolymer dispersions. The latter patent teaches the simultaneous addition at a steady rate of a stream of monomer and a stream of catalyst to an unsaturated polyol, while the former patent teaches charging the monomer and the polyol to a reaction vessel, heating the charge and thereafter adding the catalyst to the charge. Optionally, the polyol, monomer and catalyst can be added to a reactor and heated to initiate the polymerization. The present invention relates to an improvement in the preparation of the graft copolymer dispersions described in the aforementioned patents.